Shimano says the new brake system is 20-percent more powerful than Dura-Ace 7900. The improvement comes first from the caliper design, which uses a shorter arm and a symmetric, dual axle to pivot the pads toward the brake surface. The new polymer-coated brake pad and improved ergonomics further increase power. The calipers are designed for wider, 23mm rims, which are becoming more common. For the widest rims commonly found on road bikes—28mm—Shimano will sell thinner pads as an aftermarket accessory. The new group also includes a direct-mount caliper, designed to be mounted under the chainstays, for bikes that prioritize aerodynamics.

Pedals Get a Facelift and Fit Options

The PD-9000 pedal is functionally the same as the current Dura-Ace pedal, but offers new graphics and fit options. For riders who require a wider stance on the bike, Shimano will sell axles that are 4mm wider. Shim kits to adjust cleat angle will also be available.

Shimano updated its cleat to pivot from the nose, instead of the center like the existing yellow cleat. The new cleat will eliminate the lateral movement that the yellow cleat allows, and will have one degree of float, instead of three.

More Durable Chain and New Cassettes

The new 11-speed chain uses PTFE plating to reduce friction and increase the chain’s life by 20 percent. There are no longer cutouts or perforations in the link sideplates, which increases the chain’s strength. Unlike the 7900 group, it can be mounted in either direction.

The cassette is now 11-speed and available in the following configurations: 11-23, 25, or 28 and 12-25 or 28.

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Designed for pro racers, this bar-end shifter option only changes the rear derailleur.

Updated Dura-Ace 9070 Di2 Sheds Weight

Shimano’s electronic system also gets a serious makeover, with a revised lever shape centered around shift buttons that are 8mm wider than previous Di2 levers—a criticism of the original Di2 group was difficulty in differentiating between the two shift buttons. 9070 adopts Ultegra Di2’s E-tube wiring, which uses narrower wires and waterproof plugs, and drops the total weight for the wiring harness from 120 to 90 grams. The new three-port junction box includes a charging port, which means you no longer need to remove the battery from your bike to charge it. This is an especially welcome feature for cyclists who will choose to use Shimano’s new internal battery option, which mounts inside the seat post. An optional five-port junction box lets riders add remote, "satellite" shifters. The whole system works with a new ANT+ compatible Flight Deck computer from Shimano.

Dura-Ace Di2 will still have an optional satellite shifter that sits on the bar tops. Called the “Roubaix shifter,” (formerly, the "climbers' switch") it’s also compatible with Ultegra Di2. Shimano will release aero bar shifters later this summer, which will also work with Ultegra Di2 systems. An additional TT shifter option was designed at the request of Shimano-sponsored WorldTour racers—instead of two buttons on each bar-end shifter, there will be just one, and both will control rear shifts—one button will handle up shifts, the other downshifts. With those shifter, the rider would shift the front derailleur from the left base-bar shifter.

You can now install firmware that will allow you to shift multiple gears by holding the buttons down, as on Campy’s EPS system. You can also program in different shift speeds and the number of gears you have on the bike, or swap the function of the various buttons.

The new electronic components are 172 grams lighter than the current group. When used with the internal battery, Shimano claims that Dura-Ace Di2 is now lighter than mechanical Dura Ace—the company says the electronic system weighs 2,047 grams, compared to mechanical’s 2,072-gram weight. Shimano adds that Dura-Ace 9070 Di2 wont be available until January 2013, and is expected to cost for $4,139.